One control device of a hybrid vehicle is disclosed in patent document 1 (JP-A-2010-241190). This control device predicts a warming-up time of an engine and a charging time of a battery at the time of cold-starting the engine and extracts a set of operating points in which an engine warming-up completion timing and a battery charging completion timing are included within a given range and performs a load operation at any one of the operating points of the extracted set.
The conditions of cold-starting the engine are not constant but are variously changed. For example, only by adding a load of generating electricity, the charging of the battery is completed before the warming-up of the engine is completed or the warming-up of the engine is completed before the charging of the battery is completed.
Regarding this, according to the control device of the hybrid vehicle disclosed in the patent document 1 (JP-A-2010-241190), the warming-up of the engine and the charging of the battery are surely completed within a given range. Hence, this can eliminate a continuous idling operation of no load and a continuous release of thermal energy by the load operation. As a result, at the time of cold-starting the engine, by decreasing a difference between the engine warming-up completion timing and the battery charging completion timing, it is possible to reduce fuel consumption at a low efficiency and hence to improve a fuel economy.
By the way, in the hybrid vehicle using an engine and a motor generator as a driving source for driving the vehicle, when the vehicle is stopped and is driven under a low-load driving condition, the engine is intermittently driven and hence the amount of heat supplied to the coolant from the engine is reduced as compared with a case where the engine is constantly driven. As a result, in the case of using heating in the winter, there arises a case where if only the amount of heat stored in an engine coolant is used for the heating, the amount of heat is short of heat for the heating. For this reason, there is introduced also a vehicle having an electric heating system mounted thereon as a heating apparatus in addition to a heater core for supplying heat for the heating taken out the engine coolant to an interior of a vehicle compartment, the electric heating system supplying heat for the heating to the interior of the vehicle compartment by making use of electricity supplied from a battery. The heater core is a heat load of consuming the amount of heat of the engine coolant and the electric heating system is an electricity load of consuming the electricity of the battery. In this regard, other heat loads mounted in the vehicle include a battery warming-up unit of utilizing the heat of the engine coolant and the like and other electricity loads mounted in the vehicle include electric power steering and the like.
Further, in the related art, an engine operating point is selected from the viewpoint of reducing fuel consumption to the lowest level on a line called an optimum fuel economy line. The optimum fuel economy line is a line connecting points in which the fuel consumption becomes minimal for a shaft output of an engine among the engine operating points which are equal to each other in the shaft output of the engine. The reason why this line is used is that a fuel economy of the vehicle is calculated as the fuel consumption to a mileage. In the other words, fuel is transformed into a shaft output at as high an efficiency as possible to thereby reduce a ratio at which the fuel is transformed into the amount of heat for heating the coolant.
However, if the amount of heat of the engine coolant and the amount of charge of the battery become short or excess depending on the state of consumption of the heat load and the electricity load, the engine operating point on the optimum fuel economy line cannot be continuously selected. In this case, in order to bring the amount of heat and the amount of charge into adequate states, as will be described below, there is a possibility that an engine operating point greatly separate from the optimum fuel economy line needs to be selected and hence fuel consumption will be increased.
For example, in a case where the amount of charge of the battery is excess or adequate and the amount of heat is short, in order to generate heat while reducing the amount of electricity generated, the ratio of the shaft output of the engine needs to be reduced to increase the ratio of an amount of heat for heating the coolant and hence an engine operating point separate from the optimum fuel economy line needs to be selected. In this case, as the ratio of the shaft output of the engine is further decreased and hence the ratio of the amount of heat for heating the coolant is further increased, an engine operating point more separate from the optimum fuel economy line is selected. This will increase the fuel consumption.
Even in a case where both of the amount of heat and the amount of charge are short, if an adequate engine operating point is not set in consideration of a balance between the amount of heat and the amount of charge, there is likely to bring about a state where only the amount of heat is short. Regarding this case, in patent document 1 (JP-A-2010-241190), as described above, a set of engine operating points are extracted in which the engine coolant temperature at the warming-up completion timing and the state of charge of battery at the charging completion timing are reached at the same time.
However, in JP-A-2010-241190, without consideration of the state of consumption of the heat load and the electricity load, the set of engine operating points are extracted in which the engine coolant temperature at the warming-up completion timing and the state of charge of battery at the charging completion timing are reached at the same time. Hence, for example, in a case where the amount of heat consumed by the heat load is especially large as compared with the amount of charge consumed by the electricity load, even if the disclosure in JP-A-2010-241190 is performed, there will be brought about a state where only the amount of heat is short. For this reason, in order to eliminate the shortage of the amount of heat, as described above, an engine operating point must be selected which is greatly separate from the optimum fuel economy line and which is hence bad in the fuel economy.
Further, even in a case where both of the amount of heat and the amount of charge are short and the amount of heat is very shorter than the amount of charge, in a case where the amount of charge consumed by the electricity load is larger than the amount of heat consumed by the heat load, the amount of charge will be reduced. Hence, even if the engine operating point on the optimum fuel economy line is continuously selected, the amount of heat and the amount of charge can be brought into adequate states.
However, since the patent document 1 (JP-A-2010-241190) does not take the state of consumption of the heat load and the state of consumption of the electricity load into account, even in this case, as described above, the set of engine operating points are extracted in which the engine coolant temperature at the warming-up completion timing and the state of charge of the battery at the charging completion timing are reached at the same time and an engine operating point in which the fuel consumption is minimal is selected from among the engine operating points of the extracted set. In the first place, the engine operating points of the extracted set are greatly separate from engine operating points on the optimum fuel economy line, so that the engine operating points of the extracted set are increased in the fuel consumption as compared with the engine operating points on the optimum fuel economy line.
Further, even in a case where the amount of charge and the amount of heat are within adequate ranges, in a case where the amount of heat consumed by the heat load is considerably larger than the amount of charge consumed by the electricity load, as time passes, a state will be brought about in which the amount of heat is short.
However, regarding this case, the disclosure in JP-A-2010-241190 is performed in a case where the amount of charge and the amount of heat are short and does not take the state of consumption of the heat load and the state of consumption of the electricity load into account, so that the disclosure in JP-A-2010-241190 is not performed in this case and hence a state will be brought about in which the amount of heat is short. For this reason, in order to eliminate the state in which the amount of heat is short, as described above, the engine operating point must be selected which is greatly separate from the optimum fuel economy line and which is hence bad in the fuel consumption, so that the fuel consumption will be increased.
Further, in a case where the amount of charge and the amount of heat are excess, it can be considered to stop driving the vehicle by the engine to thereby prevent the generation of the heat and to drive the vehicle by the motor to thereby accelerate the consumption of the electricity.
However, for example, if this control is performed when the heat and the electricity are possibly consumed by the heating, contrarily, a state will be brought about in which the heat and the electricity are short. As a result, in order to bring the amount of heat and the amount charge into adequate states, an engine operating point greatly separate from the optimum fuel economy line needs to be selected, which results in increasing the fuel consumption.